Settings not being saved

When I enter the config page, the API key is shown but the plugin is disabled and all settings are cleared: http://monosnap.com/image/7KTsz4PjFvLBa2sZWRgSUGv9iBvVvi

If I hit save, I get the option to choose the list again and choose the settings:
http://monosnap.com/image/yByOQMVa8bqgtddmy6XZ8kGVIJIsry

But then I hit save and it clears again 🙁

Any ideas? I’ve tried with different API keys.

https://wordpress.org/plugins/woocommerce-mailchimp/